DALLAS, – Heart attack patients treated with the blood-thinner enoxaparin – a low molecular weight heparin – plus a clot dissolver were significantly less likely to die or have repeat heart attacks within 30 days compared to patients who received unfractionated heparin (UFH), according to a Rapid Track article in today’s Circulation: Journal of the American Heart Association.
Patients in the study had what are known as ST-segment elevation myocardial infarctions, which are the most severe type of heart attack. “We have very encouraging data but the evidence is not yet sufficient to say that enoxaparin should be standard treatment for severe heart attacks,” says Elliott Antman, M.D., associate professor of medicine at Harvard Medical School and director of the coronary care unit of Brigham and Women’s Hospital in Boston. “However, the data suggest we should pursue a larger clinical trial.”
Enoxaparin previously has been shown to be superior to unfractionated heparin (another blood thinner) for patients with milder heart attacks (non-ST segment elevation). It can be given as a simple injection, rather than the continuous infusion required with UFH, and it does not require frequent testing of the patient’s blood clotting status.
The researchers report their findings from the ENTIRE-TIMI 23 study. This international study involved 483 patients who presented with severe heart attacks at hospitals in the United States and Europe. Participants were randomly assigned either standard reperfusion with a full dose of the clot-dissolving drug tenecteplase (TNK) or combination therapy with abciximab and a half dose of TNK and either unfractionated heparin (UFH) or enoxaparin. Abciximab is a drug that helps keep blood platelets from sticking together to form clots.
The study was designed to evaluate enoxaparin as adjunctive treatment with various forms of reperfusion therapies (TNK, abciximab). To evaluate reperfusion (blood flow) researchers used the TIMI grading system, whereby a score of 0 means no flow through an artery and a score of 3 represents normal flow. Other objectives of the study included monitoring ST-segment resolution (normalization of the heart’s electrical activity), the effect of treatment on the risk of death or recurrent heart attack within 30 days, and the occurrence of major bleeding within 30 days.
The two blood-thinning agents achieved nearly identical rates of TIMI-3 flow at 60 minutes: The overall rate was 50 percent among all patients who received UFH and 51 percent for patients who received enoxaparin. “This finding is reassuring to doctors, because it means we don’t lose any of the benefits we have grown accustomed to seeing with unfractionated heparin,” says Antman.
The 30-day analysis of clinical events showed a significant advantage for the newer blood thinner, as 4.4 percent of enoxaparin-TNK patients had died or experienced a recurrent heart attack, compared to 15.9 percent of patients who received UFH-TNK. The rates were 6.5 percent with UFH-abciximab-TNK and 5.5 percent with enoxaparin-abciximab-TNK. Major bleeding events occurred in 2.4 percent of UFH-TNK patients and 1.9 percent of enoxaparin-TNK patients. Among patients who received the combination, the rate of major bleeding was 5.2 percent with UFH and 8.5 percent with enoxaparin.
“Our study findings, coupled with other research, will help determine whether enoxaparin should replace UFH in a variety of medical therapies for heart attack patients,” says Antman.
A new study, ExTRACT-TIMI 25, should help answer the question of whether enoxaparin can replace UFH in heart attack treatment, says Antman.
Co-authors include: Hans W. Louwerenberg, M.D.; Hubert F. Baars, M.D.; Jan C. L. Wesdorp, M.D.; Bas Hamer, M.D.; Jean-Pierre Bassand, M.D.; Frederique Bigonzi, M.D.; Ghislaine Pisapia; C. Michael Gibson, M.D., M.S.; Hein Heidbuchel, M.D., Ph.D.; Eugene Braunwald, M.D.; and Frans Van de Werf, M.D., Ph.D.
NR02 – 1033 (Circ/RapidTrack/Antman)
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